The present invention relates to a method and device for forming a shed of warp yarns for filling insertion within a weaving machine. Shed-forming devices are well known in the art and have been used for thousands of years. Shed-forming devices in the past have been mechanical in nature.
The most common production weaving machines utilize a harness and cam system. The harnesses are frames with a plurality of heddles, each heddle having a warp yarn pass through its eye, thereby allowing the harness to control the warp yarns placed within its heddles. Usually anywhere between two to eight harnesses, each having different warp yarns within its heddles, are used within a weaving machine depending on the complexity of the pattern to be woven. The harness frames rest on oblong or other geometric-shaped cams that rotate off-center on an axis. As the cams turn, the harnesses raise and lower at different intervals within the weaving machine causing the warp yarns controlled by each harness to move with that harness as that harness rises and falls, thereby forming a shed of warp yarns for the insertion of filling yarns into the fabric.
The shed usually changes after each filling insertion, meaning that at least one harness must change from its current position to a new position. Therefore, in current typical production speeds in a wide range of weaving operations, the shed, and hence the harnesses' positions, change anywhere from 300 to 1500 times per minute depending on the weaving operation.
For more complex weaving patterns, a dobby system may be attached to the weaving machine to permit more control over the harnesses, and thus the shed.
A jacquard loom allows even more control of individual warp yarns, and thus allows the weaving of the most complex patterns. A jacquard head controls each individual heddle within a jacquard loom. A series of punch cards, or now a computer program, communicates to the jacquard head which heddles to raise and which to lower. Jacquard looms operate at a slower speed than the weaving machines utilizing harnesses.
The shed-forming operation in the current state of the art places a large amount of stress on the warp yarns. The tension created among the warp beam, the raising and lowering of the harnesses, and the take-up roll causes a relatively large amount of friction on the warp yarns as they travel over the edges of the heddle eyes in both weaving machines utilizing harnesses and jacquard looms. A slashing or sizing process in which the warp yarns are run through a sizing bath to add strength and reduce hairiness must occur on most fabrics before the warp yarns are beamed onto the warp beam used in the weaving process. In some incidences, the warp yarns are run through the slashing process more than once. This slashing process is time-consuming and the chemicals used are expensive. Even after the warp yarns are run through a slasher, warp breaks occur. These warp breaks are time-consuming to fix and can cause off quality fabrics which must be sold at reduced prices. Reducing the amount of chemicals used in slashing while decreasing the amount of warp breaks would be beneficial to any weaving operation.
Further, the shed-forming operation in the current state of the art is a bottle-neck to the weaving operation in many cases. In weaving machines that utilize air jet or water jet filling insertion mechanisms, the weaving operation is not limited to the speed of the filling insertion, but rather to the speed in which the harnesses can be raised or lowered to change the formation of the shed while not destroying the warp yarns. The production of a weaving machine could be dramatically increased if the speed at which a shed can be formed can be increased.